Conclusion

After all the tests are complete it's evident that performance differences between the MG278Q and MG279Q are fairly small. Color, grayscale and gamma accuracy are similar enough that it will be hard to tell the two apart in a side-by-side comparison. The all-important input lag and response tests are so close that even the quickest gaming hands won't be able to discern between them. In fact, the only tests where the more-expensive screen won decidedly were contrast and viewing angles.

Obviously off-axis image quality is a strength of IPS and a weakness of TN. We maintain that 28 inches is the absolute maximum practical size for a TN panel. Anything larger will suffer from poor detail and color shifts at the sides even when viewed from the front. IPS on the other hand can be much bigger with no visible degradation in image quality. And it works better in two- and three-display installations.

In the case of the MG278Q, we saw the expected result in our photos of test patterns but during actual use, gaming and otherwise, there was nothing to tip us off to the fact that we were looking at a TN monitor. Shadow detail stayed consistent in all areas of the screen even when the image was very dark. It was easy to see every nook and cranny of the freighter in the opening scenes of Crysis 3, for example.

The only area where the more expensive MG279Q has a clear advantage is contrast. Not only did our calibrated test results differ by over 28 percent, we could see the extra depth in the IPS panel's black levels. Both monitors have similar brightness so it comes down to the quality of darker material. No LCD monitor renders a true black; it's always some shade of gray. But if you nit-pick about contrast the way we do, the MG278Q gives away a little quality for its lower price.

Last is the difference in FreeSync range. Both monitors will run at 144Hz but only the MG278Q can stay in FreeSync mode up to that number; the MG279Q tops out at 90Hz. To run faster you'll need to use V-Sync or simply lock the max framerate to 90 in your game. Is that a big deal? That depends on the speed of your video card.

In our system, the R9 285 we use can't run above 100fps at QHD resolution in any title, so for us the limitation doesn't matter. But if you've invested a lot of cash in a high-end AMD graphics board, the MG278Q may be a better fit. If you can push QHD resolution up to 144fps, the choice is clear.

So if you need FreeSync operation up to 144Hz, and you'd like to save a few bucks in the process, and you don't mind using a high-quality TN panel, then the MG278Q is a great choice. We enjoyed gaming with it and think you will too.

The last time I tried an ASUS 1440p panel was with their PB278Q (60Hz IPS). The first one I got had terrible back light bleed on the left side and two dead pixels right in the middle. Couldn't live with that. So I returned it and got another. The second one was sealed up on backlight bleed (good enough for the typical PLS/IPS anyway) but had four dead pixels, two which were close together on the center right side and the other two in different spots but in the general viewing area. Again, couldn't live with it and returned for my money back.

I hope their quality control has improved, because for a $500+ monitor, any dead pixels and manufacturing tolerance defects are unacceptable. I paid a little more for a Dell U2713HM and have been happy ever since. I'll be in the market for a 1440p G-sync next year as an SLI 970 owner and would not rule out ASUS if they have improved their quality control. One thing I am not clear on is if you can select custom Free-Sync or G-Sync frequencies to better match your GPU power beyond factory monitor Hz settings (90Hz, 120Hz, 144Hz).

At speeds below 40fps, you'll need to turn on V-Sync to prevent tearing, though by that point stutter is the bigger problem. It's better to either reduce resolution or turn down the detail level to keep frame rates above 40.

Uh, what about turning on LFC? LFC will work on monitors with a good variable refresh range such as this Asus unit. I'd like to see that tested for those cases where you dip in frames occasionally.

One thing I am not clear on is if you can select custom Free-Sync or G-Sync frequencies to better match your GPU power beyond factory monitor Hz settings (90Hz, 120Hz, 144Hz).

Wait, what? As long as you're within the variable refresh rate range, you're good to go. If you want to save power and reduce the framerate on a low-demand (old) game something like FRTC should work if there's no in-game cap.

One thing I am not clear on is if you can select custom Free-Sync or G-Sync frequencies to better match your GPU power beyond factory monitor Hz settings (90Hz, 120Hz, 144Hz).

Wait, what? As long as you're within the variable refresh rate range, you're good to go. If you want to save power and reduce the framerate on a low-demand (old) game something like FRTC should work if there's no in-game cap.

No what I'm talking about are complaints about (and this was from G-sync users) that they couldn't set a custom refresh rate to something like 100Hz or 110Hz in the Nvidia control panel on a G-sync monitor to better match their GPU power FPS and cap it. Maybe something's changed or they didn't know what they were talking about (or doing).

I don't have one so I can't comment. I overclock my 1440p monitors to 75Hz (Dell) and 90Hz (Crossover) and cap frames accordingly, but just have never been clear on what that meant to a G-sync monitor that advertises 120Hz/144Hz capability.

No what I'm talking about are complaints about (and this was from G-sync users) that they couldn't set a custom refresh rate to something like 100Hz or 110Hz in the Nvidia control panel on a G-sync monitor to better match their GPU power FPS and cap it. Maybe something's changed or they didn't know what they were talking about (or doing).

I don't have one so I can't comment. I overclock my 1440p monitors to 75Hz (Dell) and 90Hz (Crossover) and cap frames accordingly, but just have never been clear on what that meant to a G-sync monitor that advertises 120Hz/144Hz capability.

I'm not sure I fully understand your concern but, if I may, I'll give it a try.
As a user of Asus PG278Q (with G-sync) for a year now, I can tell you this much:
G-sync, much like FreeSync, works within a frame rate range, depending on the monitor and not the adaptive sync technology behind it, in my case within 30-144Hz. Between that frame rate range, the refresh rate is variable and depends on how many FPS your GPU can push.
This is where the similarities between the two stop because outside of that range the two technologies behave differently. Below the minimum range, 30 FPS in my case, the G-sync module automatically displays the same frame twice, making the frame rate appear double than what it is and the gameplay feel smoother. At the other end, G-sync module automatically caps your frame rate to the maximum refresh rate of your monitor (144 in my case).

That being said, having nothing to do with these adaptive sync technologies, Radeons do have a frame rate target control feature in the Catalyst control center (or whatever it's called nowdays) for power savings reasons, feature that you don't have as a Nvidia user.

Now, regarding your concern, a custom refresh rate simply defeats the purpose of having an adaptive sync technology and, outside of power savings reasons, I fail to see how a custom refresh rate target would help since G-sync (and FreeSync for that matter) already cap the refresh rate of your monitor "to better match their GPU power FPS".
If you prefer a custom refresh rate, you can chose do simply disable G-sync and set your (G-sync enabled) monitor to a fixed refresh rate (in my case I have the following options: 24, 60, 85, 100, 120, 144 Hz).
I hope that was helpful.

At speeds below 40fps, you'll need to turn on V-Sync to prevent tearing, though by that point stutter is the bigger problem.

This technically isn't true any more, if you are using the Crimson driver and have a panel with a maximum refresh rate that is 2.5 times greater than the minimum (e.g. 144Hz panels).

AMD refers to this new tech as Low Frame Rate Compensation (LFC), and it effectively does the same as Nvidia's solution (although by different means) by duplicating frames to maintain the refresh rate above a minimum refresh value (such as 40Hz). I've been playing around with it on my 390X and my Acer XG270HU and it's been working great, no stutter or hitching, just the usual expected loss in fluidity from going that low in the first place.